1. Field of the Invention
This invention relates to an electronic buzzer with piezoelectric element and more particularly to an acoustic piezoelectric vibrator for producing a comfortable buzzing sound.
2. Description of the Prior Art
In conventional buzzer apparatus, an acoustic vibrator employing a piezoelectric element vibrates with its peripheral portion free and unsupported.
This type of vibrator is not effective to have a low quality factor Q and also needs a higher voltage power source to obtain the intensity of sound in comparison with a vibrator which has its peripheral portion fixed or supported.
In addition, most prior art electronic buzzers generate a monotonic buzzing sound and they would need complicated circuitry for providing a variation of tone.
The resonant frequency fn of a circular vibrator whose peripheral portion fixed at a supporting member is maybe expressed by the following: EQU fn.alpha.t/a.sup.2
, where t is the thickness of the vibrator and a is the radius of the vibrator.